1. Field of the Invention
The invention relates to an optical proximity correction (OPC) method, and more particularly relates to an OPC correction recipe of an optical proximity correction method.
2. Description of the Related Art
OPC methods are used to eliminate critical dimension variation of lithography masks during fabrication. The transfer of original patterns to a semiconductor substrate is corrected using a software program involving computations, in which different patterns from the original patterns are obtained. The patterns corrected by OPC are then transferred to a mask. After the OPC correction, the pattern formed by light passing through the mask and irradiating the semiconductor substrate is similar to the original pattern.
FIGS. 1A and 1B show correction steps of a conventional optical proximity correction method. Referring to FIG. 1A, after an OPC model is established, the step of correcting the layout pattern according to the OPC model is conducted. An edge of a pattern on the mask is divided into a plurality of segments and each segment is defined to have a target point used as a reference when correcting the layout patterns. The segment is corrected inwardly or outwardly according to comparison with the target point reference. When defining the segments, the conventional art typically defines target points 101, 102 and 103 and dissection points 104 and 105 on the edge of the pattern of the mask. Each segment is defined according to the target points, which are calculated using the OPC model and the inward or outward corrected degree is determined accordingly. As shown in FIG. 1B, the above steps allow the target points 101, 102 and 103 to pass the after development inspection (ADI) pattern profile 110. It is noted that the conventional OPC art determines the first target point 102 and the first dissection point 104 of the critical region 106, such as the corner region of a polygon pattern or an end of a line, according to experience, wherein only the conformity is emphasize. As well, the distance from the first target point 102 to the first dissection point 104 is constant, and the segment corresponding to the first target point 102 is fixed. In addition, the inward or outward amount of the corrected segments (segments from vertex 108 to the first dissection point 104) is also constant in the conventional art and only the ADI profile 110 passing through the first target points 102 is of concern.
Although the conventional art allows exposure of patterns with good conformity, the lithography process window, however, is not taken into account. Therefore, the resulting mask layout still has deficiencies.